[sdiy] STM32 vs WM8731

Wed Feb 17 12:25:14 CET 2016

Yep, I’m familiar with Olivier’s stuff after doing the Through Holes Clouds. I’m still having an internal battle of whether that was the right thing to do, but it’s what got me the on the path of STM32 vs WM8731.

I wasn’t aware of Erics board, that looks really good. I’ll have a dig through for some pointers if that’s okay with Eric? 

Rob Spencer
gmsn.co.uk
07590 267835

From:  Synth-diy on behalf of Julian Schmidt
Date:  Wednesday, 17 February 2016 09:21
To:  <synth-diy at dropmix.xs4all.nl>
Subject:  Re: [sdiy] STM32 vs WM8731

 you could also have a look at oliviers elements repository.
 There you'll find schematics and code for a module that uses the stm32f4 and the WM codec.
 https://github.com/pichenettes/eurorack/tree/master/elements

 or at erics codec board
 http://ebrombaugh.studionebula.com/synth/stm32f4_codec_v2/index.html

On 17.02.2016 09:42, Rob Spencer wrote:

Thanks for the advice everyone. I tried to initiate a write to 0x00 and still no luck.

Here’s the setup I’m using at the moment:

https://www.dropbox.com/s/27qcwate85vuofd/2016-02-17%2008.35.57.jpg?dl=0

It’s a homebrew Morpho shield that fits onto the top of the Nucleo:

https://www.dropbox.com/s/fq1bthc74bthbct/2016-02-17%2008.36.09.jpg?dl=0

I’m going to do some checks around the board based on the suggestions below.

One quick question I’ve got is around the clock speed for the I2S MCK. In the I2S standard it mentions 2.5MHk, however STM32CubeMX wants at least 48MHz to run at 48KHz, even more if its running at 96KHz. Does that sound about right? It feels a bit high and if it is I’m really into new territory here in terms of PCB layout, but that’s the fun part, right? 

Many thanks again

Rob Spencer

gmsn.co.uk

07590 267835

On 16/02/2016 15:17, "Synth-diy on behalf of Eric Brombaugh" <synth-diy-bounces at dropmix.xs4all.nl on behalf of ebrombaugh1 at cox.net> wrote:

I've brought up a *lot* of systems with the WM8731 over the years. 

Getting the I2C control interface working can be a pain.

Your HAL I2C command looks right at first glance and the schematic seems 

OK too, so it's probably something else. One thing that you haven't 

described is what the physical construction approach is. On the WM8731, 

you'll notice that the MCLK input pin is right next to the I2C SCL pin - 

I've found that the I2C SCL input is *extremely* sensitive to crosstalk 

from the MCLK signal and if you built this on a solderless breadboard, 

or with flying wires from the MCU to codec then you can easily swamp it 

out to the point where you get no ACKs.

If you have a scope with high impedance probes, look at the SCL input 

pin - if you see MCLK there at a low level, it's a good bet your WM8731 

can't hear the I2C bus due to the crosstalk. Reroute the signals or put 

a simple RC lowpass filter on the MCLK to mitigate that.

Eric

On 02/16/2016 01:37 AM, Rob wrote:

 Just continuing on the STM32 discussions…

 I’ve been trying to get a Nucleo-F411RE talking to a WM8731, but not

 having much luck getting it to communicate over I2C

 I send the following from the STM32:

                  WM8731Status[0] = HAL_I2C_Master_Transmit(&hi2c1, 0x34,

 WM8731PowerOn1, 1, 10000);

 But I don’t get an Ack from the WM8731:

 https://www.dropbox.com/s/yhen98n17pyrqgr/Screenshot%202016-02-16%2008.22.15.png?dl=0

 Here’s the schematic for the WM8731 setup:

 https://www.dropbox.com/s/e6fkerkmf95ldzf/Screenshot%202016-02-16%2008.20.29.png?dl=0

 I’m pretty sure everything on the STM32 side is setup correctly, and I’m

 working on the assumption that there’s not a lot to do with the WM8731.

 Once all the power is connected and the I2C mode and address pins are

 set low it should just receive I2C messages. I think the issue might be

 around the address, but I’ve tried all combinations I can think of.

 Any help would be much appreciated as my wife is getting tired of me

 shouting at the darn thing!

 Many thanks in advance

 Rob

 gmsn.co.uk

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